The installation of pipe in underground service is accomplished by various methods. These methods include digging a trench mechanically or manually digging using a shovel. After a trench is dug, the pipe is usually pulled underground by means of a chinese finger. A chinese finger is a hollow wire mesh tube which encircles and grips the outside of the pipe. One end of the chinese finger is then attached to a motive device or pulling vehicle. The attachment on the motive device or pulling vehicle usually includes a shank or ripper which precedes the chinese finger in the earth. See FIG. 1, (Prior Art). The ripper R opens a trench in the earth within which the chinese finger F pulls the pipe P. Once installation is completed the chinese finger F is then removed from the end of the pipe P.
Removal of the chinese finger from the pipe is difficult since the pipe is usually in the trench covered with earth. The chinese finger must be forcibly compressed to cause it to loosen its grip on the pipe. This manual maneuver is difficult when the mesh is compacted with soil. Further, the end of the pipe may be damaged during pulling. Finally, the nature of the chinese finger requires the tool to be under tension to perform as desired. The chinese finger cannot be used to "back" pipe into tight areas where the motive device cannot be operated.
There remains a need for a pipe puller which (1) allows the puller to be quickly and non-destructively detached from the pipe after pulling; (2) protects the end of the pipe during the underground pulling operation; (3) allows the pipe to be pushed as well as pulled so as to allow installation in areas where the motive device cannot physically go, such as against a wall; (4) allows the pipe to be pulled without damaging the pipe; (5) facilitates compaction of the soil during the pulling operation so that the pipe can move freely through the earth; and (6) which has a locking grip which holds the pipe while it is pulled. The present invention addresses all six requirements by using a tapered, threaded, expandable internal gripper having an external protective cover.